rtw88: Add delay on polling h2c command status bit

On some systems we can constanly see rtw88 complains:
[39584.721375] rtw_pci 0000:03:00.0: failed to send h2c command

Increase interval of each check to wait the status bit really changed.

Use read_poll_timeout() macro which fits anything we need here.

Suggested-by: Kalle Valo <kvalo@codeaurora.org>
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200407073331.397-1-kai.heng.feng@canonical.com